Gove is an idiot! It is not going to be helpful - piecemeal changes aren't going to cut it in a helpful way until all the underlying issues are soundly addressed!!
I don't think it matters whether numbers or letters are used as long as everyone understands the system.
No system is perfect.... There is a strong political thrust to any education changes-for years they have changed the syllabus and the grade boundaries where anyone being moderately able gets top marks. The education system looked amazing if you stood far enough away from it.... There was a massive increase in passes - no one had become cleverer, there were still good and bad teachers....
This just doesn't happen in a norm referenced system. For example when I took a levels, there were no AS, everything depended on terminal exams @ end of upper sixth. out of every year nationally a percentage, about 10 per cent would get highest /lowest and everyone else would be b/c/d. The results were on a gaussian distribution. Three Cs were good grades and you would get into a reasonable uni. Only the most academically able would take a levels.
O levels in the early 1970s were graded numerically - then changed to a-c as passes based on a normative referenced system when I took them. Only 1/4 took o levels these were terminal exams - there was no coursework - students had several weeks of exam hell with 8+ subjects being examined at same time. Pity if you had awful hay fever with no non drowsy medication.
the rest took cse's which were 1-5, with 1 being the top mark and broadly eqiv to an o level grade c-ie a pass.
When the changes came in for GCSEs - it was a complete dream - here you could endlessly retake modules/have loads of help with coursework to make sure you got top marks.
This was clearly a bad move they eventually realised as you can't discriminate the truly able from the plodders who will understand it eventually... if enough time /attempts are thrown their way!
These are the people who then have to have remedial classes at uni as they just don't understand..... This never happened previously..
The old systems were not good in any generation, the new one, no better... What Gove is introducing.... Futile attempt to undo previous systems..